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Gold is heavy, with a specific gravity of 19.3 times that of water. The old timers made use of this property
when separating gold particles from sand and gravel in placer deposits using pans and sluices.
In the past, it was common to have high denomination coins minted out of gold. The milled edge around
coins is there for a reason. It was to help stop the illegal practice of shaving the edges of coins to obtain
“free” gold. The milled edge is still used on coins today even when made from non-precious metals. This
gives them the appearance of value. As time passed the value of gold contained within the coin
eventually surpassed its face value by hundreds of times. This resulted in gold coins being sold as bullion
or melted down into ingots.
With the advent of electronics last century the use of gold in electrical circuitry and wiring has becoming
increasingly important, particularly as integrated circuits are miniaturized to fit into smaller and
smaller devices. The ability to draw gold out into extremely thin wire and its resistance to oxidation
makes it ideal for this purpose.
One other use for gold is in dentistry where it is used for fillings.
Where is it found?
Gold is found in many different mineral deposit types and settings. These include epithermal,
mesothermal, porphyry, volcanogenic massive sulphide (VMS), iron oxide copper gold (IOCG) and placer
deposits, just to name a few.
Coarse-grained gold is commonly found in association with quartz (Figure 1). Quartz veins containing
gold were targeted by old time prospectors as they were relatively easy to spot while walking across the
land.
Gold can combine with sulphides, such as pyrite and arsenopyrite, in the form of extremely fine micron-
sized grains. When in this form, metallurgists often have difficulty in recovering all the gold from the ore.
In the Victorian goldfields of Australia, extremely large nuggets are found in near surface deposits.
These can be several kilograms in weight and are thought to have formed in situ by the transport and
deposition of gold in suspension.
“Gold is where you find it!”
There is phrase often used in gold exploration; “Gold is where you find it!” Its location within deposits can
be quite elusive at times. Campaign drilling of a mineralised shear or vein can often miss high grade
shoots due to their narrowness, much to the disillusionment of the geologist in charge.
Figure 1: Gold within quartz.
Figure 1: Gold within quartz.
Volcanogenic Massive Sulphide (VMS) Base Metal Deposits
Nearly a quarter of the world’s zinc production is from volcanogenic massive sulphide (VMS) deposits.
In Canada, approximately half of country’s zinc production is from VMS deposits that also supply 40% of
Canada’s silver production. VMS deposits also yield significant amounts of lead, silver, copper, and gold.
Volcanic massive sulphide deposits are accumulations of metal sulphides that precipitate from heated
hydrothermal fluid associated with volcanically active under-sea environments.
Ore Minerals
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